What are the three principles of free hand drawing?

I think that the best way to draw is to use h pencils for the out lines.

I normally use 2H for outlines and then 6B to 3B for shading(5B comes out a little better than 6B what i my opinion is.

2B, B i hardly use cause softer ones i find better.

the H pencils are for fine detail and the higher the number, the darker it becomes so for out lines I chose 2H as the best one.

B pencils are more for shading.

Obviously the lower the number in front of B the harder the led.

I will never forgive myself for all my pictures I have done with just HB.

now after using all different kinds i have realised that it is much better

But there is not such thing as 'this is how to use them & this is how not to use them"

It is up to you how you do it, experiment, you will find out yourself what you find the best ones for which part.